The West Indian Black Forms of the Genus Cœreba

Abstract

AMONG the West Indian members of the genus Ca?,reba are two peculiar forms, one known as Cwereba atrata (Lawr.) from the island of St. Vincent, and the other, C. wellsi (Cory), from the island of Grenada, which are entirely black. MIr. Ridgway has suggested (Proc. U. S. Nat. Mus., Vol. VIII, 1885, p. 28) that these may prove to be merely phases of plumage of the normally colored birds inhabiting the same islands, and I shall in the present paper advance reasons for this supposition. In the genus Careba, all the species are (except in these two cases) dark above, with a light superciliary stripe, and yellow, or yellow and white, below. Mlost of them have a yellow or yellowish patch on the rump, and all have the bases of the primaries (forming a wing spot) and the tips of the outer rectrices white. It is evident then, that the genus has a definite and well marked color-pattern. In the black forms there is an olive tinge on the underparts (except the throat) and rump, corresponding to the yellow markings of the normally colored birds inhabiting the same islands. The black forms are of the same color from the first appearance of feathers, and not of more normal coloration in the younger stages as we might expect were these forms simply species widely divergent from the generic type. The black birds are identical in size, coloration of naked parts, actions, notes, and nesting habits with the normal birds of the same islands. In the case of Ccereba wellsi the eggs are exactly alike.1 In the genus Caereba no two species are known to inhabit the same locality. In certain mammals (for example, Canis occidentalis Rich., Vulpes fulvus Desm., and Sciurus carolinensis Gmel.) melanistic